Pesticide powders, their use and preparation

ABSTRACT

An at least partially water insoluble powder containing a pesticide in admixture with an inert diluent wherein the pesticide is incorporated within the powder during its formation. The powder can be manufactured by directly admixing the pesticide, i.e., an insecticide, a larvacide, a fungicide, a herbicide, etc., or mixtures thereof, with or without the aid of pre-solution in an organic diluent, into a metalloid or metallic chloride; reacting the resulting mixture in atomized form in a stream of air with an atomized water solution of ammonia or ammoniacal substance in substantially stoichiometric proportion to the chloride to produce a fume; collecting the fume as a powder; and utilizing such activated powder as a pesticide by placing the pesticide below the surface of the earth.

This is a continuation application of application Ser. No. 722,309,filed On Sept. 10th, 1976 and now abandoned, which is a continuationapplication of Ser. No. 607,347, filed on Aug. 25th, 1975 and nowabandoned, which in turn is a divisional application of Ser. No.376,467, filed July 5th, 1973 and now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a pesticide powder wherein the pesticide isreleased, in a metered fashion, over a prolonged period of time, and aneffective method for using this powder.

The admixing of pure pesticides with inert powder for control of insectsby subsequently spreading the mixture directly on the ground or byspreading from air-borne vehicles is known. A major disadvantage ofadmixing pesticide with "inert" powder is the care which must be takento insure good mixing, particularly when using liquid pesticides,wherein loss of some volatile pesticides can occur. Further, thesepowders have good initial kill, but have little residual effect whensubjected to rain or the flow of ground waters.

Other known systems of distributing pesticides include the spraying ofwater solutions thereof; the direct atomization of relatively undilutedpesticide in situ in very low volume; and thermal volatization andfuming of a mixture of the pesticide in a "fuel" oil to create a fog.The latter system requires pesticides which are thermally stable.

To obtain a residual effect, pesticides which have an inherent long-timepersistence have been used. After many years of use some of thesepesticides, such as D D T, are proving to be ecologically undesireable.

Another form of pesticides is illustrated in German Pat. No. 871,981.This patent describes a smoke or mist that is formed by reacting mistforming components which have dissolved therein a pest combating agent.This mist is applied directly to the air as it is formed. The referencefails to recognize that the mist can be collected and used forsubsurface or subsequent application.

SUMMARY OF THE INVENTION

For simplicity, in the following specification, the term "pesticide" isused to denote an insecticide, a larvicide, a herbicide, a fungicide,etc., or mixtures thereof which are useful in killing undesirable plant,insect, fungus, etc., growth.

An object of this invention is to provide as a composition of matter apesticidal powder, which has the pesticide internally bound to itsparticles such as by absorption, adsorption, occulsion and surfacetension in a direct "one-step" reaction phase, in admixture with aninert diluent to provide a controlled dosage method.

Another object of the invention is to provide a process to directlyproduce a collected pesticidal powder with little or no thermaldegradation of the pesticide.

Another object is to provide a method for effectively using pesticidalpowder to produce a high initial kill with a protracted residual effect.

Other objects will become apparent in the course of the followingspecification.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based in part on the surprising discovery thatthe powdered particles collected as bulk mass from a chemically producedfog of a pesticide wherein the pesticide is incorporated in the powderduring its formation, give an unexpectedly high initial kill whenapplied directly below the surface of infested ground; and, that itsefficacy lasted much longer than that obtained by other methods usingthe same pesticide.

In addition, the pesticide, (i.e., insecticide or fungicide) can beapplied as a coating such as a dust to a seed prior to planting the seedin the ground.

An example, silicon tetrachloride (SiCl₄) when atomized into aircontaining atomized aqua ammonia or ammonia vapor, quickly produces afog or fume of finely divided solid, dry appearing particles. It hasbeen found that silicon tetrachloride, although a completely inorganicchemical, seemingly dissolves a variety of organic-based pesticides forform a substantially clear solution. This admixture may also be a clearemulsion, or a very stable, non-settling collodial suspension.Apparently no chemical reaction takes place during the mixing, since norise in temperature, nor evolution of gases, or precipitates wereobserved. On further experimentation, it was found that for manydifficulty soluble pesticides, pre-solution of the pesticide in anorganic solvent before admixture with the silicon tetrachloride,effected the formation of a clear solution.

Using a SiCl₄ -pesticide solution for reaction with ammonia vapor atambient temperatures as described, a cold fog was produced whichexhibited good pesticidal value when collected and used below thesurface in an insect infested area. Field tests of subsurfaceapplication of the cold fog showed excellent immediate kill (zero count)of insect, and markedly improved average residual effect for thepesticide used.

Samples of the fog were collected as a bulk fluffy powder forapplication testing by filtration, and settling in still air. Thesesamples were unexpectedly apparently "dry" powders despite the fact thatliquid pesticides and diluents had been used in the formulations. Onchemical analysis, the pesticide content in the powder were high.

Some of the collected powder was incorporated into larvae infestedmarshy and swampy ground at a depth of about 1-3 inches and spread onthe watery surface in a mosquito infested area. A large reduction inthose insects was immediately noted. Days afterward, it was unexpectedlyfound that the insecticidal and larvicidal effect was still at a highlevel (i.e., low number of insects present) long after the insectdestroying effect that would be obtained by an air-borne fog, or anultra-low-volume dispersal of the insecticide would have been depleted.Tests showed that the insecticidal value at the ground level was stillexistant. For example, it was found that the pesticidal effect could beextended from 12-18 hours to 3-4 days or more.

DESCRIPTION OF PREFERRED EMBODIMENT

To more clearly illustrate and describe a preferred method for theproduction of the powder utilized in the present invention reference ismade to the attached schematic flow diagram.

In the FIGURE the pesticide 1, (pre-dissolved in an organic diluent 2 ifrequired to solubilize the pesticide), is added to silicon tetrachloride(SiCl₄) 3, to give an admixture of SiCl₄, pesticide, and, if used,diluent 4. Ammonia (NH₃) 5 and water 6 are combined to give a watersolution of ammonia (aqua ammonia) 7. Metering pump 10 draws admixture 4through conduit 8 and into flexible conduit 8a positioned within thepump. Simultaneously, metering pump 10 draws the ammonia solution 7through conduit 9 and into flexible conduit 9a within the pump. In apreferred embodiment, a commercially available metering pump 10 exerts acommon and simultaneously peristaltic action on flexible conduits 8a and9a thereby forcing the respective liquids into conduits 11 and 12.Conduits 8a and 9a are of a proper, predetermined diameter so that thepredetermined quantities delivered by each conduit at each peristalticstroke yield an ultimate, substantially stoichiometric reaction betweenthe NH₃ and SiCl₄ in the presence of the atomized water. In thepreferred embodiment, flexible and squeezable conduits 8a and 9a areremovably connected to conduits 8 and 11, and 9 and 12 respectively sothat various size conduits 8a and 9a can be used as required and can bediscarded when their usefulness ceases. Conduits 11 and 12 lead to spraynozzles 13 and 14 positioned within air-stream conduit 15. Blower 16propels a stream of air through conduit 15 which picks up the spray andvapors from nozzles 13 and 14. Chemical reaction starts in conduit 15and is completed in reaction chamber 17 and produces a dense fume of thereaction products. The reaction chamber may be constructed with baffles17a to knock out any massive liquid droplets and to further promotereaction by turbulence. The fume produced by the chemical reaction iscarried by the air stream through conduit 18 to the collector 19 whichmay be a filter bag unit or an electrical precipitator. In collector 19the fume is removed from the air stream, and the resultant clear airpasses through conduit 20 to stack 21, or preferably through by-pass 22to be returned to blower 16 for recirculation through the system. Thequantity of recirculated air is controlled by dampers 23 and 24 locatedin stack 21 and by-pass 22 respectively. The collected powder 25 isremoved through air lock or valve 26 to container 27. Material that wasremoved or knocked down in reaction chamber 17 is eliminated throughvalve or discharge opening 28. One method to quickly and thoroughlydilute and mix the active powder from the reaction chamber 17 with aninert powder is to position container 28, containing an inert powderover air intake 29. Container 28 is directly connected to blower 30,which is connected by air conduit 31 to nozzle 32 positioned in conduit18. The inert powder, as controlled by valve 33, is fed into the blower,and the resultant stream of air propels the inert powder into the mainairstream in conduit 18. The resultant mixture of inert powder andactive powder is relatively uniform and ultimately collected incollector 19.

In the apparatus and procedure illustrated quantities of powders may beprepared with many variations in formulations. Pesticides, with andwithout organic diluents, were admixed with SiCl₄ to form various liquidmixtures. The products of reaction are passed through bag filters and/oran electrical precipitator which collects a fine fluffy, white powderwhich to all intents and purposes was "dry". In one embodiment, thestream of air is stilled, and the fume settles very slowly to form afine powder on the surfaces of the stilling or collection chamber.

In any event, the collected powder, when incorporated below the surfaceof earth containing larvae or insect eggs, will kill or prevent thegrowth of the eggs or larvae to active insects.

In many instances the quantity of powder required for efficient kill wassmall in volume. In order to enhance its handling, the active powder isextended by admixture with various inert powders such as precipitatedcalcium carbonate, ground limestone and diatomaccous earth. The extendedpowder exhibits the same characteristics and efficiency as unextendedpowder per given concentration of active powder per area of groundcovered.

In one embodiment, a solution of monoethylamine in water is substitutedfor the stoichiometric quantity of aqua ammonia. The resultant powdercontains ethylammonium chloride, and gives substantially the sameresults as powder produced using aqua ammonia. Similar results may beobtained by substituting an amine or an amine like substance such asmorpholine (tetrahydro-1,4 oxazine) for the ammonia. Similarly a watersolution of ammonium compound such as ammonium carbonate can besubstituted for the stoichiometric equivalent of ammonia required.

In some preparations, titanium tetrachloride may be substituted forSiCl₄ in the formulation. In this embodiment, after the reaction tookplace, the resultant collected powder acts essentially in the samemanner as powder produced using silicon tetrachloride.

The reaction forming the fume due to the interaction of silicontetrachloride, ammonia and water may be represented as follows:

    SiCl.sub.4 +4NH.sub.3 +2 H.sub.2 O+ excess water→SiO.sub.2 (H.sub.2 O).sub.x +4NH.sub.4 Cl

The SiO₂ produced is believed to be hydrated, as in silica gel. Much ofthis reaction takes place in the vapor phase, thus producing a cloud offinely divided hydrated SiO₂ and NH₄ particles. Reaction which takesplace within the atomized droplets probably create larger fumeparticles. A major constituent of the cloud is ammonium chloride. Forpractical purposes, the respective weights may be considered as above 2parts by weight of ammonium chloride to one part by weight ofnon-hydrate SiO₂.

It is believed that, when the pesticide is admixed with the silicontetrachloride before chemical reaction as above, the reaction in theintimate presence of the pesticide causes the pesticide to be intimatelybound to the particles of ammonium chloride and hydrated silicon dioxidesuch as by occlusion, absorption, adsorption and surface tension. Itcould be that a larger portion of the pesticide is carried by the silicaportion of the powder as by the ammonium chloride despite the oppositeratio of weights, because of the added bulk of the SiO₂ due to itshydration and the known absorptive properties of silica produced by coldchemical reaction. The diluent, if used, acts closely similar to thepesticide.

In this regard, it must be noted that the pesticide must be incorporatedinto the powder during the formation thereof. If the powder is firstmade and pesticide then added thereto inferior results are obtained.

It is further theorized that the high immediate kill is the result ofthe rapidly and easily soluble ammonium chloride quickly releasing thepesticide on first contact with moist earth; and the far longer lastingresidual effect comes from the pesticide which is very slowly releasedfrom the pores of the insoluble silica gel.

It is also believed that certain very effective pesticides which arenormally quickly degraded by earth contact, are protected by enclosingthe pesticide in the silica gel, and thus take on a longer effectiveresidual action without the non-degradeable characteristic of somepresently frowned upon insecticides such as D D T.

Because of the importance of residual kill, as well as initial kill, thepowder produced must be at least partially water insoluble. "At leastpartially water insoluble," refers to powders that contain a mixture ofwater soluble and water insoluble components (i.e., NH₄ Cl and SiO₂) ora powder that has a relatively water insoluble component that willremain intact in the soil for at least 2-3 weeks without dissolving. Thepowders can include an organic resin having bound therewith pesticidesas well as the inorganic compounds mentioned. Further the powders mustbe microporous to insure controlled metering of the pesticide into thesoil.

The invention will be illustrated in greater detail by reference to thefollowing examples which show formulations within the scope of theinvention and their method of preparation.

EXAMPLE 1

Three hundred (300) cubic centimeters of SiCl₄ are mixed with fivehundred (500) cubic centimeters of malathion previously dissolved in twohundred (200) cubic centimeters of kerosene. The resultant mixture isreacted according to the apparatus and process set forth in the attachedFigure with three thousand (3000) cubic centimenters of a 6% solution ofNH₃ in water. The apparatus is operated for approximately 10 minutesduring which time the flow of air is approximately 500 cubic feet aminute at a linear velocity of approximately 1000 feet per minute at thespray nozzles; and substantially less in the reaction chamber and in thecollecting chamber.

The powder collected weighs over 1000 grams and appears to by "dry".

Approximately 15 grams of the powder are very carefully spotted aroundon a 40×100 plot of ground heavily infested with insect larvae and adultmosquitos at a depth of 1-6 inches. At the end of 8 hours, a zero countof mosquitos is obtained at the center of the plot. At the end of 48hours, a sample of the earth is visually larvae-free. The mosquito countis still virtually zero at ground level 6 days later. The earth isessentially larvae free 2 weeks later.

The above 15 grams of powder presents some difficulty in spreadingevenly. Accordingly, another 15 grams of the powder are mixed with 1pound of precipitated calcium carbonate powder to facilitate handlingand this mixture is used below the surface on an adjoining plot of equalsize. The results obtained on mosquitos and larvae are substantially thesame as obtained for the non-extended powder.

Another 15 grams of active powder are mixed with 1 lb. of kieselguhr(diatomaceous earth), and scattered below the surface on still anotheradjoing plot of equal size. The results on mosquitos and insect larvaeare substantially the same as obtained with calcium carbonate.

EXAMPLE 2

One hundred and fifty cubic centimeters of malathion and 150 cubiccentimeters of fenthion are mixed with 300 cc of silicon tetrachloride.This mixture is reacted with 3000 cc of 6% ammonia solution and theproducts of reaction are collected. The amount of air circulated in theapparatus is increased to twice the quantities and velocities, and therate of feed of the reactants is slowed to one fourth that illustratedin Example 1. The collected powder when used in a field test exhibitsthe same characteristics as in Example 1.

In the apparatus of the Figure, items 28, 29, 30, 31 and 32 are used ina repetition of the above example to blow approximately 50 pounds offine diatomaceous earth into the main stream of air and reactionproducts in conduit 18. The resultant collected mixed powder of activepowder and inert diatomaceous earth exhibits the same characteristics asthe products of Example 1.

EXAMPLE 3

Zineb (technical grade) is difficult to dissolve in silicontetrachloride. A solution of 300 grams of zineb in 500 cc oftrichloretylene, however, readily dissolves in 300 cc of silicontetrachloride. Accordingly, this mixture is used in the reaction andprocess as set forth in Example 1 using 1800 cc of aqua ammoniacontaining 10% NH₃. A portion of the resulting powder is tested on asmall patch of ground with results similar to Example 1. Three weekslater, a sample of the soil is still practically larvae free.

EXAMPLE 4

Three hundred (300) cc of a herbicide, 2, 4-D, (2.4,-dichlorophenoxyacetic acid) are dissolved in 300 cc of heavy aromatic spirits. Theresulting solution is added to 400 cc of silicon tetrachloride. Thereaction and process are carried out as set forth in Example 1 using2000 cc of ammonium carbonate water solution containing the equivalentof 12% NH₃. After collection, the resulting powder is used below thesurface on a plot having a considerable growth of broad-leaved plants,within a week, the broad-leaved plants are destroyed, and no regrowth isapparent for seven weeks thereafter.

Other examples similar to those noted above, are made using variousinsecticides, fungicides, larvicides and herbicides, with and withoutpresolution in organic solvents, and with and without dilution of theactive powder with inert powders. The examples are on both laboratoryand semi-field scale.

The efficacy of the collected products of reaction is so great in manycases that the quantity required for relatively large areas of ground isvery small. To improve the handling and non-caking qualities of thepowder and to facilitate the spreading thereof the active powder isdiluted or extended by admixing with an inert powder such asprecipitated calcium carbonate, ground limestone, dry plaster of paris,diatomaceous earth, etc; with results that will compare to resultsobtainable in the field and laboratory with a proportionate amount ofnon-extended active powder.

The ammoniacal reactants are variously water solutions of ammonia (aquaammonia) ranging from 2% NH₃ to commercial available 26% NH₃. Bestresults appeared to be obtained with 5% to 12% solutions. Similarly insome tests, a solution of technical grade ammonium carbonate issubstituted for equivalent moles of ammonia. In other tests, ammonia gasis introduced into the air stream simultaneously with an adjacent sprayof water. Good reactions took place, but are, with the apparatus used,more difficult to control. In a number of tests, organic materials of anamine nature such as mono diethylamine or morpholine dissolved in water,are used in proportional quantities (mole) in place of ammonia.

Analysis of active powders shows a good recovery of the originalquantity of pesticide used as based on the percentage recovery of theproducts of the reaction.

Recovery of the products of reaction, that is, the collection of theactive powder, can be achieved by means of settling in still air, byfiltration media such as filter bag equipment, and by electricalprecipitation. In some cases, it is found that the dryness of the powderand its non-caking qualities are enhanced by carrying out the process ina slightly heated air stream.

Examples of some of the various insecticides, larvicides, fungicides,herbicides, etc., and the formulations that can be used for reactant 4in the process illustrated in the Figure are enumerated below. In theseformulations and other used, the insecticides, etc., were generally oftechnical or commercial grade and are referred to in most cases by theirwell-known trade names for simplicity. For example, the trade name"Malathion" refers to [(S-1,2bis(ethoxycarboayl)ethyl-O,O-dimethylphosphorodithioate]; "Nankor-8" is O,O-dimethylol O-2,4,5trichlorophenyl phosphorosulphonate; D D T is dichloro diphenyltrichloroethane; Cidial is ethyl ester of Acid O,odimethyldithiophosphoril-1-sonil acetate; etc.. The chemical formulascorresponding to various trade-name pesticides are well known to thosetrained in the art.

Examples of Reactant 4 of the FIGURE

(1)

250 cc Nankor-8

200 cc Kerosene

350 cc SiCl₄

(2)

600 cc Malathion

400 cc SiCl₄

(3)

600 cc Chlordane

100 cc Kerosene

300 cc SiCl₄

(4)

200 gr Dieldrin

450 cc Benzene

350 cc SiCl₄

(5)

250 gr D D T

500 cc heavy aromatic spirits

300 cc SiCl₄

(6)

250 gr Lindane

500 cc Trichloroethylene

300 cc SiCl₄

(7)

300 cc Chlordane

150 gr Lindane

500 cc SiCl₄

(8)

700 cc Cidial

300 cc SiCl₄

(9)

200 gr Endrin

500 cc Benzine

300 cc SiCl₄

(10)

500 cc Dursban

500 cc SiCl₄

(11)

400 cc Parathion

500 cc SiCl₄

Other formulations besides those given as examples above are used. Thepesticides are used separately in the formulation with silicontetrachloride, or in various combinations to obtain combined effects.

In a series of other tests, an equivalent mole proportion of titaniumtetrachloride is substituted for the SiCl₄ in a number of formulations.The process of making the active powder is then followed using astoichiometric amount of 10% ammonia. A powder is produced whichexhibited larvicidal and insecticidal properties to a considerabledegree. In one test, the same technique is used with stannictetrachloride with similar results. In two tests a water solution ofaluminum sulphate is admixed with water soluble pesticide such as Fundalor Carzol and reacted with ammonia gas using extremely fine sprays andheated air in the apparatus. A good fog is produced. The bulky powdercollected shows the presence of aluminum oxide (probably hydrated),ammonium sulphate and larvicide. The powder exhibited larvicidal andresidual properties to a high degree. A similar experiment with an ironchloride solution plus pesticide yields essentially equivalent results.

The examples given above are by way of illustration to show the manyvariations and modifications within the scope of this invention, but notin way of limitation.

We claim as our invention:
 1. A method for producing a pesticidalcomposition of matter which comprises:(a) passing a first streamcomprising aluminum sulfate in aqueous solution, a metallic chloride orsilicon tetrachloride to a first conduit; (b) passing a second streamcomprising ammonia, an amine, or an ammonium compound in water insubstantially stoichiometric amount to said first conduit; (c) admixinga compound or compounds selected from the group consisting of aninsecticide, a larvicide and a fungicide with one of said first orsecond streams; (d) passing a third stream comprising air through saidconduit to contact said first stream and said second stream; (e) passingthe resultant mixture to a reaction chamber maintained near ambienttemperature; (f) passing the resultant reaction mixture to a separationchamber; and (g) removing said pesticidal composition from saidseparation chamber.
 2. A method as in claim 1 wherein said first streamis silicon tetrachloride or titanium tetrachloride and said secondstream is ammonia in water.
 3. A method as in claim 1 wherein saidcompound or compounds selected from the group consisting of aninsecticide, a larvicide and a fungicide is dissolved in said firststream.
 4. A method as in 3 wherein said compound or compounds selectedfrom the group consisting of an insecticide, a larvicide and a fungicideis first dissolved in an organic solvent before admixture with saidfirst stream.
 5. A method for producing a pesticidal composition whichcomprises:(a) passing a first stream comprising silicon tetrachloride,titanium tetrachloride, tin tetrachloride, iron chloride in aqueoussolution or aluminum sulfate in aqueous solution to a first conduit; (b)passing a second stream comprising a water solution of ammonia,monoethylamine, morpholine, ammonium carbonate or ammonia gas and waterspray in a substantially stoichiometric amount to said first conduit;(c) admixing a compound or compounds selected from the group consistingof an insecticide, a larvicide and a fungicide with one of said first orsecond streams; (d) passing a third stream comprising air through saidconduit to contact said first stream and said second stream; (e) passingthe resultant mixture to a reaction chamber maintained near ambienttemperature; (f) passing the resultant reaction mixture to a separationchamber; (g) removing said pesticidal composition from said separationchamber by means of settling, filtration or electrical precipitation;and (h) removing air from said separation chamber and recycling at leasta portion of said air to said first conduit.
 6. A method as in claim 5wherein said compound or compounds selected from the group consisting ofan insecticide, a larvicide and a fungicide is dissolved in said firststream.
 7. A method as in claim 5 wherein said compound or compoundsselected from the group consisting of an insecticide, a larvicide and afungicide is first admixed with an organic solvent selected from thegroup consisting of trichloroethylene, heavy aromatic spirits, keroseneand benzene, before admixture with said first stream.
 8. A method as inclaim 5 wherein a fourth stream comprising an inert extender of calciumcarbonate, diatomaceous earth, ground limestone or dry plaster of parisis admixed with said reaction mixture prior to its passing to theseparation chamber.